immunology of the eye

Question 1

Name the physical (2), chemical (5) and cellular (3) barriers to infection that exist within the eye

Answer 1

-Physical
flushing + mucous layer

chemical
lysozyme
lactoferrin & transferrin
complement
tear lipids
secretory IgA

Cellular
neutrophils- release free radicals
macrophages- phagocytosis of damaged cells
conjuntival mast cells- vasoactive mediators

Question 2

Describe the acquired immune system in the following:

• conjunctiva (4)
• cornea and sclera
• vitrous, choroid and retina

Answer 2

-lymphatic drainage (only part of the eye where this occurs)
dendritic cells act as antigen presenting cells
mucosa associated lymphoid tissue present (MALT)
commensal bacteria

-avascular due to collagen coats
no lymphatics
down regulated immune environment and lack of APCs

-blood ocular barrier exists
down regulated immune environment and lack of APCs

Question 3

what is immune privilege?

• why does it exist?
• mechanims
• name for systemic tolerance to an antigen presented in the anterior chamber

Answer 3

• certain sites can tolerate introduction of antigens without eliciting an inflammatory immune response
• need to minimise collateral damage that occurs with inflammation

-due to blood barrier and lack of direct lymphatic drainage
ocular microenvironment is rich with immunosuppressive molecules

-ant chamber assoc immune deviation (ACAID)

Question 4

What is sympathetic opthalmia?

mediated by what cells

Answer 4

bilateral granulomatous uveitis due to trauma/surgery on one eye
occurs secondary to autoimmune reaction to ocular antigens exposed during trauma
mediated by T cells (CD4 Th cells then CD8 cytotoxic T cells)
injured eye= exciting eye, contralateral eye is the sympathising eye

Question 5

give 5 examples of wye in which the immune system can dysfunction

Answer 5

recurrent infection
allergy
autoimmune disease
cancer
transplant rejection

Question 6

type I hypersensitivity

• define
• give opthalmic example
• symptoms

Answer 6

• immediate hypersensitivity, IgE mediated
• acute allergic conjunctivitis
• itchy, erhythematous, swollen, chemosis

Question 7

type II hypersensitivity

• define
• give opthalmic example
• appearance
• treat

Answer 7

• Direct cell killing, cytotoxic by macrophages/NK cells
• Ocular cicatricial pemphigoid:

-blistering disease so get blisters around the eyes & scarring, adhesions between lids and cornea damaged
increased vascularisation

-Steroids and immunomodulation

Question 8

type III hypersensitivity

• define
• give opthalmic example
• appearance
• treat

Answer 8

• immune complex mediated
• autoimmune corneal melting

-cornea becomes opaque and outer layers melt away
thin inner layer and risk of perforation

-steroids

Question 9

type IV hypersensitivity

• define
• give opthalmic example
• appearance

Answer 9

• Delayed type hypersensitivity, T cell mediated
• corneal graft rejection
• vascularisation, the graft becomes hazy and can no longer see